JP5716507B2 - Surface light source device and image display device - Google Patents

Description

  The present invention relates to an optical member that changes the traveling direction of light, a surface light source device using the optical member, and an image display device using the surface light source device. In particular, when the surface opposite to the unit optical element forming side is made to be a fine uneven surface to prevent optical adhesion, an optical member that can eliminate both the occurrence of moire and luminance unevenness due to the fine unevenness, and the optical member The present invention relates to a surface light source device used and an image display device using the surface light source device.

  A surface light source device used for an image display device includes a light source and a plurality of optical sheets (optical films) that change the traveling direction of light from the light source. Examples of the optical sheet include a light collecting sheet that narrows the traveling direction of light in the front direction and improves the front brightness in the front direction, a light diffusion sheet that diffuses light source light and makes an image of the light source inconspicuous. And the surface light source device implement | achieves desired front luminance and a viewing angle, and makes the image of a light source inconspicuous by combining a condensing sheet | seat and a light-diffusion sheet | seat suitably.

  As the condensing sheet, an optical sheet is generally used in which linearly extending unit optical elements are arranged in a direction orthogonal to the longitudinal direction (so-called linear arrangement). The unit optical element typically has a triangular, semi-elliptical, or semi-circular cross-sectional shape in a cross-section (also referred to as a main cut surface) orthogonal to the longitudinal direction.

Moreover, the optical sheet needs to prevent the back surface on the opposite side to the surface on which the unit optical elements are formed from being in optical contact with other optical members.
For this reason, for example, in Patent Document 1, a minute protrusion for forming a gap whose height is not less than the wavelength of the light source light and not more than 100 μm is formed on the back surface opposite to the prism surface where triangular prism unit prisms and the like are arranged as unit optical elements. We have proposed many optical sheets arranged randomly. By providing such a microprojection group without making the back surface a mere smooth surface, when other surface smooth optical members such as a light guide plate and an image display panel are arranged adjacent to the back surface of the optical sheet, Problems such as non-uniform luminance in-plane distribution due to optical contact with other optical members, interference fringes, light wetting (also referred to as wet out, uneven luminance in wet bleeding), and the like can be prevented. As a result, in-plane luminance non-uniformity due to optical contact, interference fringes, and the like can be effectively prevented. Further, the microprojection group can provide an effect of making the light source image invisible by the light diffusion action.

  However, the light diffusing action by the microprojection group also has one aspect that the front luminance is lowered and the screen of the image display device becomes dark when applied to the image display device. For this reason, Patent Document 2 proposes an optical sheet in which transparent hemispherical projections called convex dots are arranged vertically and horizontally on the back surface opposite to the surface on which unit optical elements are formed in order to improve the front luminance. doing. Since the transparent hemispherical protrusion also has a light collecting function, the front luminance is improved. However, if the hemispherical protrusions are arranged in a grid pattern in a certain cycle in the vertical and horizontal directions, the arrangement period of the hemispherical protrusions interferes with the arrangement period of pixels such as liquid crystal panels or unit prisms, and moire tends to occur.

  As described above, Patent Document 3 and Patent Document 4 describe an optical sheet that prevents the occurrence of moire by periodically arranging microprotrusions arranged on the back surface opposite to the surface on which the unit optical elements are formed. An optical sheet that eliminates moire and improves front luminance by arranging cuboidal microprojections randomly on the back surface as microprojections has been proposed.

Japanese Patent No. 3518554 JP-A-6-102506 Japanese Patent No. 2855510 Japanese Patent No. 2764559

  However, moiré is eliminated and front luminance is improved by forming a minute uneven surface in which cuboid-shaped minute protrusions are randomly arranged on the back surface opposite to the unit optical element forming surface proposed by Patent Document 3 and Patent Document 4. Even when the brightness is improved, uneven brightness may occur due to the random density of the microprojections.

  That is, an object of the present invention is to achieve both the elimination of moire caused by the fine unevenness and the elimination of luminance unevenness for an optical member provided with fine unevenness on the back surface opposite to the unit optical element forming surface. Moreover, it is providing the surface light source device and image display apparatus using the optical member which eliminated this moire and brightness irregularity.

Therefore, in the present invention, a surface light source device and an image display device having the following configurations are provided.
(1) A light source and an optical member placed on the light exit surface of the light source, wherein the optical member is a sheet-like main body and a large number of unit optics arranged on one surface of the main body An element and a minute protrusion formed on the other surface of the main body, and the minute protrusion is a large number when viewed from a normal direction perpendicular to the sheet surface of the sheet-like main body. And the mesh pattern has an average value N of the number of boundary line segments extending from one branch point, and 3.0 ≦ N <4.0, and The surface light source device , wherein the opening region includes a region having a pattern in which a direction having a repetition period does not exist, and the minute protrusions are convex with respect to the opening region at a portion of the mesh pattern.
(2) An image display device comprising the surface light source device according to (1 ) above and an image display panel placed on a light output surface of the surface light source device.

  According to the present invention, the optical member that changes the traveling direction of the light beam by the unit optical element is formed on the back surface opposite to the unit optical element forming surface, from the minute protrusion having no periodicity unique to the present invention. Due to the minute uneven surface, optical adhesion can be prevented without causing moire or luminance unevenness. Therefore, it is possible to prevent optical moistness while achieving both moire elimination and luminance unevenness elimination.

The perspective view explaining one Embodiment of the optical member by this invention. Sectional drawing which illustrates the shape of a unit optical element. The top view which shows an example of the planar view shape of a mesh pattern. The top view explaining that a repetition period does not exist in a mesh-like pattern. The figure which shows the method of determining a generating point in the method of designing a mesh pattern. The figure which shows the method of determining a generating point in the method of designing a mesh pattern. The figure which shows the method of determining a generating point in the method of designing a mesh pattern. The figure explaining the degree of dispersion | distribution of the determined mother point group by an absolute coordinate system and a relative coordinate system. The figure which shows the method of creating a Voronoi diagram from the determined generating point and determining a mesh pattern. The top view which shows an example by which the mesh pattern was repeated as a unit pattern area | region of the magnitude | size of 1/3 or more of the dimension of the formation surface of the fine protrusion in an optical member. The top view which shows the net-like pattern which comprises the micro protrusion of the optical member of this invention. The top view which shows the pixel arrangement | sequence of an image display panel. The top view which shows the state which accumulated FIG. 11A and FIG. 11B. The top view which shows the optical member (A) which has a regular pattern, the pixel arrangement | sequence (B) of an image display panel, and the state (C) which accumulated these. Sectional drawing which shows the various examples of the main cut surface shape of the mesh-shaped pattern which comprises a micro protrusion. Sectional drawing which shows the example of a form of the surface light source device by this invention. 1 is a cross-sectional view illustrating one embodiment of an image display device according to the present invention.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are conceptual diagrams, and the scale relations, aspect ratios, and the like of components may be exaggerated as appropriate for convenience of explanation.

[A] Definition of terms:
Hereinafter, definitions of main terms used in the present invention will be described here.

“Sheet surface” means a surface that coincides with the planar direction of the optical member 10 when the sheet-like optical member 10 is viewed as a whole and globally (in the case of an uneven surface, it also corresponds to an envelope surface). To do. In this case, the “sheet surface” is also a surface parallel to “one surface 1 p” or “the other surface 1 q” of the main body 1.
“One surface 1p” of the main body 1 is a virtual surface that does not exist as a surface when the unit optical element 2 is completely filled with no gap.
When the surface of the optical member 10 on the side having the unit optical element 2 is shown, it is called an “optical element surface”, and the surface on the opposite side and having the minute protrusions 3 made of the mesh pattern 3P is referred to as the “back surface”. "
The “main cut surface shape” is defined as a cross section orthogonal to the extending direction when the extending direction exists in the element of interest among the cross sections parallel to the normal line standing on the sheet surface of the optical member 10. This means the shape at the “main cut surface”.
“Cross section” when simply referred to as “cross section” or “cross section shape” means a cross section parallel to a normal line standing on the sheet surface of the sheet-like optical member 10.
The “planar shape” means a shape on a plane parallel to the sheet surface of the optical member 10. In other words, the “planar shape” means a shape when the optical member 10 is viewed from the direction of the normal line that stands on the sheet surface.

“Smooth” means smooth in an optical sense. That is, here, it means the degree that a certain proportion of visible light is refracted while satisfying Snell's law on the light incident surface or light output surface of the optical member 10. Therefore, for example, if the ten-point average roughness Rz (JISB0601: 1994 version) of the other surface 1q of the main body 1 is equal to or shorter than the shortest visible light wavelength (0.38 μm), it is sufficiently smooth.
The terms “sheet”, “film” and “plate” are not distinguished from each other based solely on the difference in designation. Therefore, for example, a “sheet” is a concept including a member that can also be called a film or a plate.

[B] Optical member:
First, an optical member according to the present invention will be described with reference to an embodiment shown in the perspective view of FIG.

1A and 1B, the optical member 10 of the present invention illustrated in one embodiment of the present invention has a large number of unit optical elements 2 arranged in a regular arrangement on one surface 1p of a sheet-like main body 1. The other surface 1q of the main body 1 is provided with a minute protrusion 3 made of a mesh pattern 3P unique to the present invention.
In the embodiment shown in the figure, the unit optical element 2 is a unit triangular prism having a shape in which the main cutting plane is an isosceles triangle and the base is the main body 1 side.
The mesh pattern 3P constituting the minute protrusion 3 has a large number of boundary line segments L that define a large number of opening areas A when viewed from the normal direction perpendicular to the sheet surface of the sheet-like main body 1. In the boundary line segment L, the average value N of the number of boundary line segments L extending from one branch point B is 3.0 ≦ N <4.0, and the opening region A is repeated. The pattern has a region where there is no direction having a period. The surface of the opening area A, that is, the other surface 1q is a smooth surface.
For this reason, optical contact can be prevented by the minute protrusions 3 made of the mesh pattern 3P without causing moiré or luminance unevenness.

  Hereinafter, the optical member according to the present invention will be described in detail for each component.

<Main body>
The main body 1 is a transparent member that supports the unit optical element 2 and the minute protrusions 3 and may be an inorganic member such as glass or ceramics in addition to an organic member such as a resin sheet. These may be appropriately selected from known transparent members according to the application. For example, a resin sheet made of a polyester resin such as polyethylene terephthalate, a polyolefin resin such as a cycloolefin polymer, a cellulose resin such as triacetyl cellulose, an acrylic resin, or a polycarbonate resin is used as the organic member. it can.
The main body 1 is “sheet-like”, but “sheet” is a concept including a film and a plate as described in the definition column, and is not distinguished by thickness or rigidity. For example, the thickness of the main body 1 is 25 μm to 5 mm.

One surface 1 p of the main body 1 is a surface having the unit optical element 2, and the other surface 1 q of the main body 1 is a surface having the minute protrusion 3. One surface 1p and the other surface 1q are usually parallel to each other.
One surface 1p of the main body 1 is a virtual surface that is not exposed when the unit optical element 2 is completely filled, and the other surface 1q of the main body 1 is actually an opening region A serving as an actual exposed surface. Surface.

《Unit optical element》
The unit optical element 2 has a convex shape with respect to one surface 1p of the main body 1, and a plurality of one-dimensionally or two-dimensionally arranged transparent optical elements that change the traveling direction of light. Is an element. As such a unit optical element 2, those of various known shapes can be used. For example, the unit optical element 2 arranged one-dimensionally includes columnar unit optical elements such as a columnar unit prism and a columnar unit lens, and a direction orthogonal to the extending direction (ridge line direction) of each of the columnar unit optical elements (see FIG. 1 (A) is arranged regularly or irregularly in the left-right direction). This arrangement is called a one-dimensional arrangement. The unit optical element 2 arranged two-dimensionally includes a cone-shaped unit prism such as a quadrangular pyramid, and a protruding unit optical element such as a hemispherical unit lens. Each of these protruding unit optical elements is regularly or irregularly arranged in two directions in the sheet surface (for example, the X direction and the Y direction in the XY plane). This arrangement is called a two-dimensional arrangement.
Here, the prism means an optical element whose surface (contact surface with air) is a combination of flat surfaces, and the lens means an optical element whose surface is a single curved surface or a combination of a plurality of curved surfaces.
The unit optical element 2 may be an optical element whose surface is a combination of a flat surface and a curved surface. In this case, the flat surface portion functions as a prism and the curved surface portion functions as a lens.

[One-dimensionally arranged unit optical elements]
The columnar unit prisms arranged one-dimensionally are typically triangular prism unit prisms having a main cut surface shape of a triangle {see FIG. 2 (1)}. In addition, the main cut surface shape is a pentagon {FIG. (2) Reference}, a polygonal prism unit prism such as a hexagon may be used.
As the columnar unit lens arranged one-dimensionally, a cylindrical unit lens having a shape in which the main cut surface of the surface portion forms a part of a circle or an ellipse {see FIG. 2 (3)} is representative. In addition, the main cut surface shape of the surface part is a parabola, hyperbola, cycloid, cardioid, normal distribution curve, sine curve, hyperbolic sine curve, elliptic function curve (sn function, cn function), Bessel function curve, Rankine egg shape A curved column unit lens formed of a continuous smooth curve forming a part of a curve or the like may be used.

[Unit optical elements arranged two-dimensionally]
Typical examples of the two-dimensionally arranged cone-shaped unit prisms are cones having a triangular cross section {see FIG. 2 (1)} or pyramid unit prisms. A base or a truncated pyramid unit prism may be used.
The shape of the bottom surface in contact with one surface 1p of the cone-shaped unit prism is, for example, a polygon such as a triangle, a quadrangle, a pentagon, and a hexagon, or a smooth continuous curve such as a circle and an ellipse.
As the hemispherical unit lens arranged two-dimensionally, a shape in which the cross-sectional shape of the surface portion forms a part of a circle or an ellipse {see FIG. 2 (3)} is representative, but in addition, a parabola, a hyperbola, It may have a shape that forms part of a cycloid, cardioid, normal distribution curve, sine curve, hyperbolic sine curve, elliptic function curve (sn function, cn function), Bessel function curve, Rankine egg-shaped curve, or the like.
The shape of the bottom surface in contact with one surface 1p of the hemispherical unit lens is, for example, a smooth continuous curve shape such as a circle or an ellipse, or a polygon such as a triangle, a quadrangle, a pentagon, or a hexagon.

[Deformed shape]
The unit optical element 2 may have a cross section or a bottom shape that is deformed. For example, one or both of the hypotenuses on both sides of the apex of the triangle of the cross section are bent outward or inward or curved outward or inward (see FIG. 2 (4)), and the vicinity of the apex of the triangle is curved. And rounded shape (not shown).
The unit optical element 2 illustrated in FIGS. 2 (1) to 2 (4) has a shape that is convex with respect to the one surface 1p of the main body 1. However, for example, the unit optical element 2 may be a lens. For example, in addition to a convex lens, a concave shape such as a concave lens {see FIG. 2 (5)} may be used.

[Placement style]
The unit optical elements 2 arranged one-dimensionally are, in the columnar unit optical elements 2 extending linearly, the extending directions extending linearly are parallel to each other, and usually have a constant period with respect to one direction in the sheet surface. Arranged in In addition, the extending direction of the columnar unit optical element 2 may be a curved line such as a circular shape or a wave shape, a broken line, or the like when viewed from the normal direction standing on the sheet surface.
The unit optical elements 2 that are two-dimensionally arranged are usually arranged in a regular lattice pattern with a constant period.
In both the one-dimensional arrangement and the two-dimensional arrangement, the arrangement may be an irregular arrangement in addition to a regular arrangement having a constant period.

The unit optical element 2 may be a mixture of the unit optical element 2 of the lens element and the unit optical element 2 of the prism element.
The unit optical element 2 may be a mixture of unit optical elements 2 arranged one-dimensionally and unit optical elements 2 arranged two-dimensionally.
When a large number of unit optical elements 2 are arranged, the unit optical elements 2 may have the same shape and the same size, but may have different shapes and different sizes.
By introducing irregularity into one or more of shape, size, and arrangement, when other members have a regular pattern, it is possible to prevent the occurrence of moire due to interference with the regular pattern.

[Size]
If the unit optical element 2 is a unit triangular prism, the dimensions of the unit optical element 2 are, for example, 10 to 100 μm at the base contacting one surface 1p, 10 to 100 μm in height, and 80 to 120 ° in the apex angle. The period is 10 to 100 μm.

  As described above, the various shapes and arrangements of the unit optical elements 2 are appropriately selected based on required optical functions such as condensing or light diffusion, and optical performance such as aberration of materials.

<Small ridges>
When viewed from the normal direction perpendicular to the sheet surface of the sheet-like main body 1, the minute protrusion 3 includes a mesh pattern 3 </ b> P that defines a large number of opening areas A, The mesh pattern 3P includes a region having a specific shape and a pattern in which there is no direction in which the opening region A has a repeating cycle. 1B, FIG. 3, FIG. 4 and FIG. 11A, the entire area is formed of a pattern in which the opening area A does not have a repeating cycle. The minute protrusion 3 having the mesh pattern 3P has a cross-sectional shape that is convex with respect to the opening region A at the mesh pattern 3P.

[Reticulated pattern and opening area defined by it]
As shown in FIG. 3, the mesh pattern 3 </ b> P is formed from a large number of boundary line segments L that extend between two branch points B and define an opening region A, and the boundary line segments L that extend from one branch point B. The average value N of the numbers of 3.0 is 3.0 ≦ N <4.0, that is, is 3.0 or more and less than 4.0, and is repeated in the opening region A defined by the boundary line segment L. The shape has no direction with a return period.

  Further, with respect to the mesh pattern 3P of the minute protrusion 3, the mesh pattern 3P is observed from the normal direction to the sheet surface of the sheet-like optical member 10 while mainly referring to FIGS. A description will be given in the form of a plan view.

  As shown in FIGS. 3 and 9, the line portion Lt of the mesh pattern 3P includes a large number of branch points B. The line portion Lt of the mesh pattern 3P is composed of a number of boundary line segments L that form branch points B at both ends. That is, the line portion Lt of the mesh pattern 3P is composed of a number of boundary line segments L extending between the two branch points B. Then, at the branch point B, the boundary line segment L is connected, so that the opening region A is defined. In other words, an opening area A as a closed area is defined by being surrounded by a boundary line segment L and partitioned.

  As shown in FIGS. 3 and 9, since the line portion Lt is composed of only the boundary line segment L, there is no line portion Lt extending into the opening region A. According to such an aspect, it is possible to effectively realize simultaneously imparting sufficiently low haze and high front luminance to the optical member 10.

  On the other hand, in order to prevent the occurrence of moire, the mesh pattern 3P of the optical member 10 according to the present embodiment includes a region where the opening region A does not have a linear direction having a repeating cycle. In order to surely eliminate moiré, it is preferable that the entire area of the mesh pattern 3P is composed of only such areas. The present embodiment has such a configuration. As a result of intensive research, the inventors of the present invention do not simply make the pattern of the mesh pattern 3P irregular, but the opening area A of the mesh pattern 3P has a repetition cycle with a certain regularity. By defining the pattern of the reticulated pattern 3P so that the arranged directions do not exist, the optical member having the structure in which the minute protrusions are periodically arranged and the image display panel 30 having the periodic pixel arrangement are overlapped. It has been found that possible moire can be made inconspicuous very effectively.

(No repeat cycle)
FIG. 4 is a plan view on a sheet surface parallel to the XY plane for explaining that there are no repetition periods in a large number of opening areas A defined by the mesh pattern 3P. One virtual straight line di is selected at an arbitrary position in the sheet surface at an arbitrary direction.
This one straight line di intersects the boundary line segment L to form an intersection. The intersections are shown as intersections c1, c2, c3,..., C8 in order from the lower left in the drawing. The distance between adjacent intersections, for example, the intersection c1 and the intersection c2, is a dimension t1 on the straight line di of the certain opening region A. Next, the dimension t2 on the straight line di is similarly determined for another open area A adjacent to the open area A on the straight line di. Then, with respect to a straight line di at an arbitrary position in an arbitrary direction and a boundary line segment L intersecting with the straight line di, a number of opening regions A that encounter the straight line di at an arbitrary position in an arbitrary direction are as dimensions on the straight line di. t1, t2, t3,..., t8 are determined. And the sequence of numerical values of t1, t2, t3,..., T8 has no periodicity.
In FIG. 4, these t1, t2, t3,..., T8 are drawn separately from the mesh pattern 3P along with the straight line di in the lower part of the drawing for easy understanding.
When the straight line di is rotated by an arbitrary angle from the one shown in FIG. 4 and the dimensions t1, t2,... Thus, no periodicity is observed. That is, there is no direction having a repeating cycle in the opening area A defined by the boundary line segment L as in the sequence of numerical values of t1, t2, t3,.

  Furthermore, in the mesh pattern 3P of the minute protrusion 3 of the optical member 10 according to the present embodiment, the average value N of the number of boundary line segments L extending from one branch point B is 3.0 ≦ N <4.0. It has become. Thus, when the average value N of the number of boundary line segments L extending from one branch point B is 3.0 ≦ N <4.0, the arrangement pattern of the mesh pattern 3P is shown in FIG. The square lattice pattern (N = 4.0) shown in FIG. In addition, when the average value N of the number of boundary line segments L extending from one branch point B is 3.0 <N <4.0, it is also large from the honeycomb arrangement (N = 3.0). Different patterns can be used. When the average value N of the number of boundary line segments L extending from one branch point B is 3.0 ≦ N <4.0, the arrangement of the opening regions A is made irregular so that the opening region A repeats. It has been confirmed that it is possible to prevent the directions arranged with the return period from being stably present, and as a result, it is possible to make the moire extremely inconspicuous.

  The average value N of the number of boundary line segments L extending from one branch point B is strictly the number of boundary line segments L extended for all the branch points B included in the mesh pattern 3P. The average value is calculated by checking. In practice, however, the total number of boundary line segments L extending from one branch point B is considered in consideration of the size of the opening area A per line defined by the line portion Lt. For a branch point B included in one section having an area expected to reflect the tendency (for example, a portion of 10 mm × 10 mm in the mesh pattern 3P in which the opening area A is formed in the dimension example described later) The number of boundary line segments L extending is examined to calculate the average value, and the calculated value is treated as the average value N of the number of boundary line segments L extending from one branch point B for the mesh pattern 3P. You may do it.

  Actually, in the mesh pattern 3P constituting the minute protrusion 3 of the optical member 10 shown in FIG. 3, the average value N of the number of boundary line segments L extending from one branch point B is 3.0 <N. <4.0. For example, in the case of the mesh pattern 3P of FIG. 3, when a total of 387 branch points B are measured, the boundary line segment L has three branch points B, the boundary line segment L has four boundary lines L, and the like. The number of branch points B is 14 (the number of branch line segments L to be branched is 5 or more), and the average number of boundary line segments L coming from the branch point B (average branch number) is 3.04. It was a piece.

(Moire status)
FIG. 11C shows a typical pixel arrangement in the image display panel 30 shown in FIG. 11B with the mesh pattern 3P included in the minute protrusions 3 of the optical member 10 shown in FIGS. 3 and 11A. Overlaid on top. As can be understood from FIG. 11C, when the mesh pattern 3P shown in FIG. 3 and FIG. 11A is actually produced and arranged on the pixel array of the image display panel 30, the striped pattern can be visually recognized. A pattern, that is, moire (interference fringes) did not occur.
In these drawings, the reticulated pattern 3P is drawn exaggerated black so that the pattern is easy to understand, but the actual one is a colorless and transparent one.

  Here, the pixel array of the image display panel 30 shown in FIG. 11B is a typical pixel array in the image display panel 30. As shown in FIG. 11B, in the image display panel 30, one pixel P includes a sub-pixel (sub-pixel) RP that emits red light, a sub-pixel GP that emits green light, and a sub-pixel BP that emits blue light. , Is composed of. That is, the image display panel 30 can form an image in color. In the example shown in FIG. 11B, the pixels P are formed as a so-called stripe arrangement. That is, the sub-pixel RP that emits red light, the sub-pixel GP that emits green light, and the sub-pixel BP that emits blue light are sequentially arranged in one direction (vertical direction in FIG. 11B). On the other hand, the sub-pixel RP that emits red light, the sub-pixel GP that emits green light, and the sub-pixel BP that emits blue light are arranged one by one in a direction perpendicular to the one direction (the horizontal direction in FIG. 11B). It has been. 11B shows the image display panel 30 observed from the normal direction to the image forming surface (light-emitting surface, that is, the screen) of the image display panel 30, in other words, from the normal direction to the panel surface of the image display panel 30. In this state, the arrangement of the pixels P is shown.

  On the other hand, FIG. 12 exemplifies the occurrence of moire when the opening areas A defined by the mesh pattern 3P are arranged at a predetermined repetition period. Also in this figure, the mesh pattern 3P is drawn black so that the pattern can be easily understood.

  The optical member shown in FIG. 12A is an optical member having minute protrusions 53 formed of repeating periodic patterns 53P formed in a square lattice pattern and arranged in a predetermined period in the vertical and horizontal directions. It is different from the optical member 10 of the invention. 12C shows a repeating cycle pattern 53P of the optical member 50 having the repeating cycle shown in FIG. 12A, and the image display panel 30 shown in FIG. 11B is the same as that shown in FIG. 11B). As can be understood from FIG. 12A, FIG. 12B, and FIG. 12C, when the minute protrusions 53 including the repeating periodic pattern 53P are arranged on the pixel array of the image display panel 30. Due to the interference between the regular pattern of the repeating periodic pattern 53P constituting the minute protrusion 53 and the regular pattern of the pixels, light and dark streaks (in the example shown in FIG. 12C, extend from the upper left to the lower right). Light and dark stripes) are visible.

  In the example shown in FIGS. 12A and 12C, the arrangement direction of the square lattice formed by the repeating periodic pattern 53P is inclined several degrees with respect to the arrangement direction of the pixels P. Yes. This inclination angle is referred to as a bias angle (degree). Such an inclination is a technique that is widely used in general to make moire inconspicuous. However, as can be understood from the fact that the striped pattern is visually recognized in FIG. 12C, the degree of moire generation is not determined solely by the bias angle, but in addition, the pixel P and the repeating period pattern 53P. This also depends on factors such as the repetition period ratio and the line width of the repetition period pattern 53P. In order to eliminate moire only with the bias angle of the repeating cycle pattern 53P, it is necessary to prepare optical members having different bias angles according to the design specifications of the image display panel 30.

(Method for creating pattern shape of mesh pattern)
Here, the average value N of the number of boundary line segments L extending from one branch point B is 3.0 ≦ N <4.0, and the open areas A are arranged in a repeating cycle having a certain regularity. An example of a method for producing a pattern of the mesh pattern 3P having no linear direction will be described below.

  The method described here includes a step of determining a generating point, a step of creating a Voronoi diagram from the determined generating point, and a boundary line segment extending between two Voronoi points connected by one Voronoi boundary in the Voronoi diagram. Determining a path of L, determining a thickness of the determined path, demarcating each boundary line segment L, and determining a pattern of the mesh pattern 3P (line portion Lt). Yes. Hereinafter, each step will be described in order. Note that the pattern shown in FIG. 3 described above is a pattern actually determined by the method described below.

  First, the process of determining a generating point will be described. First, as shown in FIG. 5, an absolute coordinate system O-X-Y (this coordinate system O-X-Y is a normal two-dimensional plane. The first generating point (hereinafter referred to as “first generating point”) BP1 is arranged at an arbitrary position of “. Next, as shown in FIG. 6, the second generating point BP2 is arranged at an arbitrary position separated from the first generating point BP1 by a distance r. In other words, at any position on the circumference of a circle with a radius r centered on the first generating point BP1 on the absolute coordinate system XY (hereinafter referred to as “first circumference”), the second A generating point BP2 is arranged. Next, as shown in FIG. 7, the third mother point BP3 is arranged at an arbitrary position away from the first mother point BP1 by the distance r and away from the second mother point BP2 by the distance r or more. Thereafter, the fourth generating point is arranged at an arbitrary position separated from the first generating point BP1 by the distance r and from the other generating points BP2 and BP3 by the distance r or more.

  In this way, the mother point is arranged at an arbitrary position away from the first mother point BP1 by the distance r and away from the other mother points until the next mother point cannot be arranged. Go. Thereafter, this operation is continued based on the second generating point BP2. That is, the next generating point is arranged at an arbitrary position separated from the second generating point BP2 by the distance r and from the other generating points by the distance r or more. Based on the second generating point BP2, until the next generating point cannot be arranged, it is at an arbitrary position away from the second generating point BP2 by the distance r and from the other generating points by the distance r or more. Place the mother point. Thereafter, the base point as a reference is sequentially changed, and the base point is formed in the same procedure.

  With the above procedure, the mother point is arranged until it becomes impossible to arrange the mother point in the region where the mesh pattern 3P is to be formed. When the generating point cannot be arranged in the region where the mesh pattern 3P is to be formed, the step of generating the generating point ends. By the processing so far, the mother point group irregularly arranged on the two-dimensional plane (XY plane) is uniformly dispersed in the region where the mesh pattern 3P is to be formed.

With respect to the generating point groups BP1, BP2,..., BP6 (see FIG. 8A) distributed in the two-dimensional plane (XY plane) in such a process, the distances between the individual generating points are not constant. Have However, the distribution of the distance R between any two adjacent generating points is not a complete random distribution (uniform distribution), but a range ΔR between the upper limit value R _MAX and the lower limit value R _MIN with the average value R _AVG in mind. = R _MAX -R _MIN is distributed. Note that, here, if two Voronoi regions XA are adjacent to each other but two Voronoi regions XA are adjacent to each other after a Voronoi diagram is generated from the generating point groups BP1, BP2,... It is defined that the generating points of are adjacent to each other.

That is, the generating point group described here is referred to as a coordinate system having each generating point as an origin (referred to as a relative coordinate system oxy, while a coordinate system defining an actual two-dimensional plane is referred to as an absolute coordinate system O. 8 (B), FIG. 8 (C),..., In which all the generating points adjacent to the generating point placed on the origin are plotted are obtained for all generating points. Then, when the graph of the adjacent generating points on all the relative coordinate systems is displayed with the origin o of each relative coordinate system superimposed, a graph as shown in FIG. 8D is obtained. The distribution pattern of adjacent mother point groups on the relative coordinate form is not a uniform distribution in which the distance between any two adjacent mother points constituting the mother point group is 0 to infinity, but the distance from the origin o. Is distributed in a finite range from R _AVG −ΔR to R _AVG + ΔR (a donut-shaped region from radius R _MIN to R _MAX ).

As described above, by setting the distance between each generating point, the Voronoi region XA obtained from the generating point group by the method described below, and further, the circumscribed circle diameter (or the opening region A) obtained from this point The distribution of the area of the opening region A) is not uniform (completely random) but distributed within a finite range.
By configuring in this way, shading (brightness and darkness) unevenness when the mesh pattern 3P is viewed is more effectively eliminated. In order to make the shading pattern of the mesh pattern 3P visible substantially invisible and compatible with the anti-moire due to the non-periodicity of the mesh pattern 3P, the circumscribed circle diameter D (open area) When the maximum value of A) is D _MAX and the minimum value is D _MIN , the circumscribed circle diameter distribution range ΔD = D _MAX −D _MIN is the average value D _AVG of D,
0.1 ≦ ΔD / D _AVG ≦ 0.6
More preferably,
0.2 ≦ ΔD / D _AVG ≦ 0.4
And

  In addition, in the process of determining the above generating points, the size of the opening area A per one can be adjusted by changing the size of the distance r. Specifically, by reducing the size of the distance r, it is possible to reduce the size of the opening area A, and conversely, by increasing the size of the distance r, The size of the opening area A can be increased.

  Next, as shown in FIG. 9, a Voronoi diagram is created based on the arranged generating points. As shown in FIG. 9, the Voronoi diagram is composed of line segments that are drawn at the intersection of two bisectors by drawing a perpendicular bisector between two adjacent generating points BP and BP. FIG. Here, the line segment of the bisector is called Voronoi boundary XB, the intersection of Voronoi boundary XB forming the end of Voronoi boundary XB is called Voronoi point XP, and the area surrounded by Voronoi boundary XB is Voronoi area XA Call it.

  In the Voronoi diagram created as shown in FIG. 9, each Voronoi point XP forms a branch point B of the mesh pattern 3P. Then, one boundary line segment L is provided between two Voronoi points XP forming the end of one Voronoi boundary XB. At this time, the boundary line segment L may be determined so as to extend linearly between the two Voronoi points XP as in the example shown in FIG. Various paths (for example, circle (arc), ellipse (arc), fence line, hyperbola, sine curve, hyperbolic sine curve, elliptic function curve, Bessel function curve, etc.) between the two Voronoi points XP without It may be extended by a broken line or the like. When the boundary line segment L is determined to extend linearly between two Voronoi points XP as in the example shown in FIG. 3, each Voronoi boundary XB defines the boundary line segment L. It becomes like this.

  After determining the path of each boundary line segment L, the line width (thickness) of each boundary line segment L is determined. The line width of the boundary line segment L is determined so that the minute protrusions 3 do not impair the original optical characteristics of the optical member 10 together with the optical adhesion prevention effect. As described above, the pattern of the mesh pattern 3P can be determined.

  According to the present embodiment as described above, the mesh pattern 3P of the fine protrusion 3 of the optical member 10 extends between the two branch points B and defines a large number of boundary line segments L that define the opening region A. The average value N of the number of boundary line segments L extending from one branch point B is 3.0 ≦ N <4.0, and the opening region A has a repetition period. Is not present. As a result, even if the optical member 10 is superimposed on the image display panel 30 in which the pixels P are regularly (periodically) arranged, the stripe pattern (moire, interference fringes) is generated to such an extent that it can be visually recognized. This can be effectively prevented.

(Repeat as unit pattern area)
Furthermore, in the above-described embodiment, there is a direction in which the opening region A defined by the mesh pattern 3P included in the minute protrusion 3 has a repetition period in the entire region of the minute protrusion 3 in the optical member 10. An example that is not to be explained. However, as shown in FIG. 10, the entire area of the mesh pattern 3P of the minute protrusion 3 in the inside is an area in which a plurality of opening areas A are arranged in a pattern without a predetermined repetition period ( A plurality of unit pattern areas S) may be aggregated to form the entire area of the mesh pattern 3P. That is, in this embodiment, the entire area of the mesh pattern 3P includes two or more unit pattern areas S in which opening area groups are arranged in the same pattern when viewed locally. . In this case, the connection between the unit pattern regions S is substantially inconspicuous and can be ignored unless there are four or more repetitions in a certain period in a specific direction. Of course, neither moire nor shading unevenness occurs in the unit pattern region S. In this example, the pattern of the mesh pattern 3P in one unit pattern region S can be created in the same manner as the pattern creation method described with reference to FIGS.
In particular, the image display panel 30 has recently been increased in size. For such a large-screen image display panel 30, the mesh pattern 3 </ b> P of the minute protrusion 3 has a plurality of unit pattern regions S. It is more preferable that the unit pattern area S includes a plurality of unit pattern areas S that are configured by arrangement and in which the opening areas A are arranged in the same pattern in each unit pattern area S. It is preferable in that the pattern creation of the pattern 3P can be greatly facilitated.

  In particular, in the example in which one type of unit pattern region S is arranged in a plurality of vertical and horizontal directions as shown in FIG. 10, there is a repetition as the unit pattern region S in a specific direction (two directions in the drawing vertical direction and horizontal direction). . In the embodiment of FIG. 10, the unit pattern region S is repeated with a repetition period SP2 in the horizontal direction and a repetition period SP1 in the vertical direction. Under these conditions, when the dimension of the unit pattern area S in a specific direction is Ls, and the unit pattern area S has N opening areas A in the dimension Ls on an arbitrary straight line dj extending in the specific direction, When attention is paid to a certain opening area A on dj, there is a regularity that there is always an opening area A having exactly the same size tj and shape at a position where the number of the opening areas A is separated by N on the straight line dj. Have. However, this regularity is based on the repetition cycle as the unit pattern region S (the dimension Ls corresponds to the repetition cycle in the above description), and is not the repetition cycle as the opening region A. In the unit pattern area S, the opening area A does not have a repetition period in the specific direction. In addition, the repetition cycle as the unit pattern region S is not close to the dimensional relationship in which moire is generated because the size is different from the arrangement cycle of the pixel arrangement of the display panel by, for example, 1000 times or more.

  In the example shown in FIG. 10, the optical member 10 is divided into six unit pattern regions S having the same shape, and the mesh pattern 3P of the minute protrusion 3 in each unit pattern region S is formed. It is configured identically. The six unit pattern regions S are arranged so that three regions are arranged in the vertical direction (up and down direction in FIG. 10) with a repetition period SP1, and two regions are arranged in the horizontal direction in FIG. Yes.

[Main cut surface shape of mesh-like pattern constituting minute protrusions]
The main cut surface shape of the mesh pattern 3P of the minute protrusion 3 is not particularly limited as long as it can prevent optical adhesion. For example, a shape as shown in the cross-sectional view of FIG. 13 is selected, the main cut surface shape of the minute protrusion 3 is a lens or prism shape, and its dimensions (base width and protrusion height) are the longest visible light spectrum of the light source light. If it is designed to function as a lens or prism as long as the wavelength is exceeded (usually 5 μm or more with some allowance), the light source light can be diffused or condensed to improve the front brightness and the viewing angle. Can also be granted. 13 (1) is a rectangle (including a square), FIG. 13 (2) is a trapezoid, FIG. 13 (3) is a part of a circle or ellipse, FIG. 13 (4) is a triangle, and FIG. 13 (5) is a triangle. A shape in which a hypotenuse of a trapezoid or a trapezoid is modulated in a convex shape toward the outside (in the case of a triangle in the figure), and in addition to this, a pentagon, a hexagon, and the like are omitted. The drawings are conceptual, and the corners of the cross-sectional shape may be rounded in consideration of modeling accuracy and shape durability in manufacturing.

[Dimensions of minute protrusions]
The dimensions of the minute protrusions 3 constituting the mesh pattern 3P are about 1 to 100 μm as the line width of the boundary line segment L constituting the mesh pattern 3P. The height of the minute protrusion 3 is the shortest of the visible light spectrum in the light source light from the viewpoint of preventing optical close contact with the other optical member having a smooth surface adjacent to the main body portion 1 of the optical member 10. The wavelength needs to be 0.38 μm or more, and more preferably, the longest wavelength of the visible light spectrum in the light source light is 0.78 μm or more. Further, even if the thickness exceeds 100 μm, the effect of preventing optical adhesion is already saturated, and there are problems such that the minute protrusions 3 are easily visible and easily broken. Therefore, the preferable protrusion height from the main-body part of the fine protrusion 3 is about 1-100 micrometers from these balance. The line width of the boundary line segment L does not have to be the same in the entire area of the mesh pattern 3P.
The size of the opening area 1A defined by the mesh pattern 3P is about 5 to 5000 μm, preferably about 10 to 500 μm, in terms of the diameter of a circumscribed circle inscribed in the opening area 1A.

[Material of minute protrusions]
The microprojections 3 may be made of a transparent material, and the transparent material is basically not particularly limited. If the main body is an inorganic material, an inorganic material such as glass or ceramics may be used. It may be used. Among these, the resin material is preferable because it can be easily formed. The transparent material may be a thermoplastic resin such as an acrylic resin, a polycarbonate resin, or a styrene resin, but is preferably a curable resin from the viewpoint of rapid solidification, and ionizing radiation that is also cured by ultraviolet rays or electron beams. It is preferable to use a curable resin. Examples of the ionizing radiation curable resin include acrylate-based, epoxy-based, and polyester-based resins.

<Method for forming unit optical element and micro-projection on main body>
The method for forming the unit optical element 2 on the one surface 1p of the main body 1 and the method for forming the minute protrusion 3 on the other surface 1q of the main body 1 are not particularly limited. It can be formed by appropriately adopting various known forming methods such as a molding method.

[Unit optical element]
It is not necessary for the unit optical element 2 to positively function the optical action with respect to the transmitted light transmitted through the one surface 1p on the one surface 1p that becomes the interface with the main body 1. Therefore, the unit optical element 2 can be molded integrally with the main body 1.
Since one surface 1p of the main body 1 is a virtual surface, the outer side (unit optical element 2 side) and the inner side of the one surface 1p of the main body 1 may be made of the same material or different. It may be made of a material.

  As described above, as a molding method for forming the unit optical element 2 on the one surface 1p of the main body 1, for example, the following molding method or a molding die can be used. The mold surface of the mold is provided with irregularities that are opposite to the unit optical element 2.

a) After applying a liquid ionizing radiation curable resin to the mold surface of the cylindrical mold, the resin sheet is pressed against the coated surface, the resin is cured on the mold surface, and then the resin sheet is peeled off. A molding method for molding the curable resin surface;
b) A melt extrusion molding method in which a molten resin extruded from a T die or the like is supplied between a cylindrical mold and a pressing roll, and the resin is cooled and solidified on the surface of the mold, thereby forming the melt.
c) injection molding method,
d) a hot press method in which a resin is sandwiched between a heated mold and a metal plate or a metal roll to heat and press, and after cooling and solidification, the mold is released;
e) A transfer method in which after the resin is laminated on the mold, the mold is peeled off and the shape of the mold surface is transferred to the resin surface.

(Configuration of main body 1 and one surface 1p)
In the description of the molding method, the case where a resin sheet and a resin material are used will be described. According to the method such as a) the molding method, the resin material is interposed between the molding die and the resin sheet. Thus, the unit optical element 2 can be molded on the resin sheet by curing the resin material in a state where the resin sheet is not in contact with the mold surface of the mold. As a result, the main body 1 is composed of a resin sheet and a resin material cured into a sheet shape. In addition, the unit optical element 2 can be molded on the resin sheet by curing the resin material while the resin sheet is in contact with the mold surface of the mold. It will be composed only of. Accordingly, the one surface 1p is the surface of the resin sheet in the latter case, and the virtual surface inside the cured resin material in the former case.

[Small ridges]
The minute protrusion 3 is formed on the other surface 1q of the main body 1 as an optical element having a planar view shape that presents a mesh pattern 3P having a convex shape with respect to the opening region A. The opening area A is an exposed surface and can be the other surface 1q of the main body 1 itself, and is usually the other surface 1q itself.
It is not necessary for the minute protrusion 3 to positively function the optical action with respect to the transmitted light transmitted through the other surface 1q on the other surface 1q that becomes the interface with the main body 1. For this reason, the minute protrusion 3 can be formed integrally with the main body 1.

Such a minute protrusion 3 can be formed by the same method as described in the molding method in which the unit optical element 2 is formed on the one surface 1p. In other words, as the mold, a mold in which the surface of the mold is formed with irregularities opposite to the minute protrusions 3 is used. At this time, since the fine ridge 3 is usually smaller in height than the unit optical element 2, the fine ridge 3 is formed first, and then the main body 1 such as a resin sheet on which the fine ridge 3 is formed. It is preferable to form the unit optical element 2 with respect to the member to be performed in that the shape of the unit optical element 2 does not collapse. However, it is also possible to prepare both molds and continuously mold the fine protrusion 3 and the unit optical element 2 on the front and back of the resin sheet in one pass with respect to the resin sheet.
In addition, the micro protrusion 3 and the main-body part 1 may be comprised from the same material, and may be comprised from a different material.

  The fine protrusions 3 may be formed by a printing method as a forming method other than the molding method. In the printing method, an image line corresponding to the mesh pattern 3P constituting the fine protrusion 3 is printed. In the printing method, an ink made of a resin material is used. As the printing method, known printing methods such as intaglio printing, silk screen printing, offset printing, letterpress printing, and ink jet printing can be employed.

<Deformation>
In addition to the above-described embodiment and configuration, the optical member 10 may have a configuration in which other components are added as described below, for example.

The main body 1 may have a light diffusion layer between the one surface 1p and the other surface 1q. The light diffusing layer can be formed as a layer in which a light diffusing agent is dispersed in a matrix. The light diffusion layer may be in contact with one surface 1p or the other surface 1q. A light diffusion function can be imparted by the light diffusion layer.
An antireflection layer composed of a low refractive index layer having a relatively lower refractive index than that of the layer immediately below may be formed on the surface of the optical member 10 as the light incident surface. The reflection loss of the incident light on the optical member 10 can be reduced by the antireflection layer.
The optical member 10 may have an antistatic layer. The antistatic layer can also be used as one or more of the main body 1, the unit optical element 2, and the minute protrusion 3. The antistatic layer provides the optical member 10 with an antistatic function, reduces adhesion of foreign matters such as dust, and suppresses adverse effects on optical characteristics.

Further, in the above-described embodiment, the entire area of the other surface 1q of the main body 1 of the optical member 10 is composed only of the mesh pattern 3P in which the opening area A does not have a direction having a repeating cycle. It was.
However, if the moire between the pixels of the image display panel and the periodic arrangement of the unit optical elements is in a range that can be substantially ignored, there is a direction in which the aperture regions A are arranged at a constant repetition period. Such a mesh pattern 3P may be adopted (of course, the opening regions A are not arranged at a constant repetition period except for such a specific direction, and other requirements of the present invention are included). Such a form is also included in the mesh pattern 3P of the present invention.

[C] Surface light source device:
The surface light source device according to the present invention includes at least a light source and the optical member 10 of the present invention placed on the light exit surface of the light source.
A surface light source device according to the present invention will be described with reference to a surface light source device 100 of one embodiment illustrated in FIG. The surface light source device 100 according to the present embodiment includes a light source 20 and an optical member 10 disposed adjacent to the planar light exit surface 20 a of the light source 20. The optical member 10 is the optical member 10 of the present invention exemplified in FIG.
Even when the optical member 10 is disposed in contact with the light exit surface 20a of the light source 20, the minute protrusion 3 provided in the optical member 10 prevents optical adhesion without causing moire or luminance unevenness.

In the present embodiment, the light source 20 is a surface light source having a flat light exit surface 20a, and a known light source can be used as the light source 20 of the surface light source.
For example, if a planar light-emitting electroluminescent panel (EL panel) is used as the light source, the light source 20 can be used as it is. Further, when using a cold cathode tube of a linear light emitter or a light emitting diode (LED) of a point light emitter as a light source, the light exit surface 20a is appropriately combined with a light guide plate, a light diffusion plate, a light reflection plate, or the like. The light source 20 is configured as an edge light (side light) type or a direct type so as to be planar. In other words, in this case, the light source 20 can also be said to be a light source module.

  When the light exit surface 20a is a virtual surface (for example, when there is a space from the light emitter to the optical member 10 with a direct surface light source), optical contact does not occur. Therefore, the effect of preventing both the moire and the luminance unevenness by the optical member 10 and preventing the optical adhesion is to the light source 20 having the actual surface where the light exit surface 20a becomes an interface between the solid object and the air. .

  The surface light source device 100 may further include other members in addition to the light source 20 and the optical member 10, and various other members known in the surface light source device can be appropriately employed as the other members. Examples of other members include a brightness enhancement film such as a polarized light separating film, a light diffusion film, a polarizing film, and a retardation film.

In the surface light source device 100, the orientation of the optical member 10 with respect to the light source 20 may be the direction in which the minute protrusion 3 side is the light source 20 side, as shown in FIG. 14A. As in (B), the unit optical element 2 side may be oriented to the light source 20 side. In the latter case, it is possible to prevent optical adhesion with an optical member such as an image display panel placed on the surface light source device 100 while preventing the occurrence of moire and luminance unevenness.
In these drawings, the light output surface side as the surface light source device 100 at the upper side of the drawing is the image display panel and the viewer V side of the image.
Further, the optical member 10 may be arranged in a stack of a plurality of sheets such as two sheets in addition to a single sheet. By arranging a plurality of sheets, for example, when the unit optical element 2 is a columnar unit optical element and the optical characteristics have directionality in the sheet surface direction, the optical characteristics having the directionality can be arranged in a plurality of directions. it can.

[D] Image display device:
An image display device according to the present invention includes at least the surface light source device 100 according to the present invention described above and an image display panel placed on the light exit surface of the surface light source device 100.
An image display apparatus according to the present invention will be described with reference to an image display apparatus 1000 of one embodiment illustrated in FIG. An image display device 1000 illustrated in FIG. 15 includes a surface light source device 100 including the optical member 10 as described above, and an image display panel 30 disposed on the light exit surface 100a of the surface light source device 100. It is. In addition to the surface light source device 100 and the image display panel 30, the image display device 1000 includes a housing (cabinet), input / output components, and the like, and, for example, in the case of a television receiver, depending on the use of the image display device. Various known parts such as a tuner are provided. These other components are not particularly limited, and depend on the application.

  The image display panel 30 is a transmissive display panel such as a liquid crystal panel that can display an image. The image display panel 30 may include various circuits such as a display drive circuit, wiring between the drive circuit and the display panel main body, a chassis, a frame, a touch panel, and the like that integrate them. Therefore, the image display panel 30 can also be called a “display module” or a “panel module”.

  By using the image display device 1000 having such a configuration, the optical member 10 is used in the surface light source device 100. Therefore, when the image display device 1000 is viewed from the viewer V side of the image, The minute protrusion 3 provided in the optical member 10 provides a device in which optical adhesion is prevented without causing moire or luminance unevenness.

[E] Application:
The optical member 10 according to the present invention is suitable as an optical member for a surface light source device, and the surface light source device 100 including the optical member 10 is suitable as a backlight of a transmissive display device. The image display device 1000 provided is suitable as an image display device for television receivers, measuring devices and instruments, office devices, medical devices, computer devices, telephones, electronic signs, game machines, digital photo frames, and the like.

DESCRIPTION OF SYMBOLS 1 Main-body part 1p One surface 1q The other surface 2 Unit optical element 3 Minute protrusion 3P Mesh pattern 10 Optical member 20 Light source 20a Light emission surface 30 Image display panel 100 Surface light source device 100a Light emission surface 1000 Image display device A Opening area B Branch point BP Generating point L Boundary line segment Lt Line part (set of boundary line segment)
S Unit pattern area V Observer

Claims (2)

A light source and an optical member placed on the light exit surface of the light source,
The optical member has a sheet-like main body, a large number of unit optical elements disposed on one surface of the main body, and a minute protrusion formed on the other surface of the main body. The fine protrusions are composed of a mesh pattern that defines a large number of opening areas when viewed from the normal direction perpendicular to the sheet surface of the sheet-like main body, and the mesh pattern is one branch point. An average value N of the number of boundary line segments extending from the region is 3.0 ≦ N <4.0, and the opening region includes a region having a pattern in which there is no direction having a repetition period, Is a surface light source device that is convex with respect to the opening region at the portion of the mesh pattern . An image display device comprising: the surface light source device according to claim 1; and an image display panel placed on a light exit surface of the surface light source device.

Images